thank you for bearing my inverse-logic-of-what´s-next questions : )
this pre deserves my ol´teeth chewing a custom case. Hope good ol´magnetic rusty steel is good for casework.
tnx
this pre deserves my ol´teeth chewing a custom case. Hope good ol´magnetic rusty steel is good for casework.
tnx
Nice project Zen....and I do need a balanced pre-amp to make my VFET-X to sing.
Following with great interest!
yup
rotary switch operating relays through flat cable
but not snap on
you'll see as soon I get them from China - usual stuff
it's hard to find economical 24 position switch outside of China - I need them for relays , not Elma or Grayhill to directly switch signal
24Vdc PSU also on switch pcb
rotary switch operating relays through flat cable
but not snap on
you'll see as soon I get them from China - usual stuff
it's hard to find economical 24 position switch outside of China - I need them for relays , not Elma or Grayhill to directly switch signal
24Vdc PSU also on switch pcb
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it's sorta more logical to grab pic from net , pronto , than to wait thingies to arrive and photograph them ......
so - something like this
as I said - no big choice of 24 pos. switches around , and pcb mount ones are available just in dreams
so - I'm gonna solder few short wires , while pcb will be mounted ditto on switch screws
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sweet macaron amp : )
An externally hosted image should be here but it was not working when we last tested it.
)
I have been trying to implement the iron-pre concept using a B1 buffer (ver 0) and a pair of telefunken transformers which I bought off ebay. I have been struggling to get the telefunkens to work as autoformers. I do not understand what I am doing wrong - a 200 mV input comes out as 20 mV at the output. However, when I wire up the telefunkens as normal transformers, I can get 200 mV at the output (or 400, if I use the 1:2 links).
I can live with using the telefunkens as transformers, but I am curious as to why I cant get the autoformer concept to work? The circuit follows closely what Zen Mod posted as attached.
The other question I have is that assuming that I am using the telefunken as normal transformers, can I drop the 10 uf capacitors (c101 and c201) from the circuit? And the 1k resistors too? (R104 and R204)
Thanks!
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I can live with using the telefunkens as transformers, but I am curious as to why I cant get the autoformer concept to work? The circuit follows closely what Zen Mod posted as attached.
The other question I have is that assuming that I am using the telefunken as normal transformers, can I drop the 10 uf capacitors (c101 and c201) from the circuit? And the 1k resistors too? (R104 and R204)
Thanks!
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post datasheet for Telefunkens and we'll see where's the catch - most probably simple phase issue
maybe faster way is - just try to swap secondary ends , in autoformer arrangement
regarding cap - no - you can't shoot DC in xformer , unless it's made for that and you're doing it deliberately .......
signal xformers are not usually made for that
so - either keep cap in signal path , or make buffer with 0Vdc offset ( complementary JFets with dual supply , or any other with same characteristics)
just don't use TL071 buffer ......
maybe faster way is - just try to swap secondary ends , in autoformer arrangement
regarding cap - no - you can't shoot DC in xformer , unless it's made for that and you're doing it deliberately .......
signal xformers are not usually made for that
so - either keep cap in signal path , or make buffer with 0Vdc offset ( complementary JFets with dual supply , or any other with same characteristics)
just don't use TL071 buffer ......
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Thanks. I did swap the secondaries and it went worse! 🙁
Unfortunately no datasheet - this is all i have :
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Unfortunately no datasheet - this is all i have :
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it must be one of these iterations - one is proper , other one is Dodo/antiphase
when you find proper one , remember that you can use any of secondary taps as OUT+ , to accommodate gain to your needs
however , if you feel uneasy about all that , you can always send them to OPLDF , for proper disposal
when you find proper one , remember that you can use any of secondary taps as OUT+ , to accommodate gain to your needs
however , if you feel uneasy about all that , you can always send them to OPLDF , for proper disposal
Attachments
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Will give it a try. After i sort out this AC hum issue which just came jn the last hour. Must be the wiring.
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I have a pair of those and they will work as Zen autoformers,
Can't remember the wiring but I set them up with a scope to be sure of phase.
Did not use them in the end as there was very little difference in sound between just passive stepped attenuator, and buffer with auto former.
Conclusion was that less is more and just passive used. 🙂
Can't remember the wiring but I set them up with a scope to be sure of phase.
Did not use them in the end as there was very little difference in sound between just passive stepped attenuator, and buffer with auto former.
Conclusion was that less is more and just passive used. 🙂